Showcasing original music is awesome and I congratulate you. To make money, you have to have people that will come to see you. It takes some time but the harder you work, the faster it'll happen. Granted , it's not a lot of money , but if you consider that you're only playing a set, $100-$300 isn't bad because it's your music and if you multiply that by three or four , it's on par with how much lower to medium level cover bands get. That is level 1 that you need to get to.
First, you should do your best to be as competitive as you can be so practice your asses off. You guys have to kill it when your onstage. You have to promote and be part of your music scene which means going to other metal shows, meeting people and introducing yourselves to anyone and everyone. This is essential for a local music scene. We'd flyer cars at gigs, hand out flyers , make friends with other bands that have an actual draw, get on local radio shows, benefits, you name it. Be good first, though. Merchandise is also important because it's great advertising. Having people help with setting up equipment and selling merch with something as simple as a folding table with a banner behind them also helps because it shows others that there are people who believe in you. This is show business and the only reality potential fans have is what their perception is. What they see, they tend to believe. Not sure your age but the younger you are , the easier it is to find people willing to do those things (a lot of times, for free because they believe in you). You know who doesn't like pre sale tickets ? Bands that can't draw because they don't have enough fans willing to pay five or ten bucks to see them. Build a fan base by continuing to showcase with other bands (include all age and underage shows because of the strong teenage metal fan base) and network until you can bring in 30 people that you know will buy a ticket before doing the pay to play thing. You just have to do it at the right time is all. Instead of balking at the roadmap, embrace it. Pay to play has been around since the eighties and it's a way for the club to know that the place won't be empty. Can you blame them ? Social media and videos are great , of course, put pictures of fans from your last show up on your Facebook page and website and keep doing so. Get Instagram, Twitter and keep up with whatever the next social media tool may be and keep moving forward. Let everyone know "hey everyone, we're putting the finishing touches on our next song called xxxxx and we'll have ready for you at our show on xxxx ". Use your imagination , humor to keep people interested with social media. I'm in my 40's now and I'll tell you, the older your potential fanbase gets, the harder it is so, go for it ! The multi band showcase is a great way to win over fans that came to see someone else as well as showing your presence in the scene. If you can be the best band that night, you win over people. Keep doing it and in a year or two, you should at least make a dent if you're any good. Gotta go, but I hope this helps.